Project Summary The optic nerve of adult humans shows little potential for regeneration or self-repair, which presents a major challenge to restoring vision in patients with optic nerve injury or diseases, including glaucoma. These patients thus suffer from the pathological consequences and vision loss for the rest of their lives. A regenerative therapy is vital for preserving sight or reversing vision loss. Yet an in depth understanding of the molecular basis that controls optic nerve growth/regeneration remains ambiguous. We here propose to investigate why the optic nerve fails to regenerate and how nerve regeneration can be enhanced to improve neuronal function after injury. Long-standing work from my and other laboratories has shown that optic nerve growth is a programed event during development whose shut-down contributes critically to the failure of optic nerve regeneration. A recent discovery in my laboratory has identified a novel potent regulator, insulin-like growth factor (IGF) binding protein like 1 (IGFBPL1) whose presence activates the growth program and regenerative process of retinal ganglion cell (RGC) axons and induces activation of IGF-1 receptor (IGF-1R) and its downstream signals. Administration of exogenous IGFBPL1 promoted optic nerve regeneration and RGC survival in adult mice; whereas, blockade of IGF-1R-induced signals, at least in culture, abolished IGFBPL1-mediated axonal growth or regeneration. This points to a central role for IGFBPL1 functioning through IGF-1R-induced intracellular events to regulate optic nerve regeneration. Importantly, IGFBPL1 as a secretory factor presents a clinically feasible candidate for manipulating nerve regeneration and restoring vision after injury in humans. This proposal thus seeks to further explore the underlying mechanisms through which IGFBPL1, particularly its relation to IGF-1R-mediated signals, promotes RGC axon regeneration. Moreover, it will evaluate the efficacy of IGFBPL1 on promoting optic nerve regeneration in an established animal model of optic nerve injury. Completion of the proposed studies will uncover a previously unknown signaling loop in IGF-1R-mediated cascades in the regulation of RGC axon growth and will advance our understanding of the mechanisms that control optic nerve regeneration and repair. This will accelerate the preclinical development of a novel regenerative therapy for currently untreatable conditions. As the optic nerve has long served as a standard model for the study of CNS injury, results may also have a broad impact on the development of new therapies to treat brain and spinal cord injury or diseases.